Aging effect on mechanical characteristics of bituminous mixtures

Traditionally, asphalt concrete requirements are based on recipe specifications for bituminous mixtures; these specifications do not consider changes in the mechanical properties of materials over time. A considerable hardening of bitumen occurs with age, a characteristic that must be considered in the evaluation of bituminous materials. In asphalt concrete evaluation work, such as pavement design or end-product contracts, the age of asphalt materials may have a considerable impact on the outcome. This investigation was undertaken to aid the development of a performance specification that is based on the structural functional properties of asphalt concrete. Properties of asphalt concrete cores from various road sections were evaluated with respect to changes in stiffness and creep over several years, with an emphasis on hardening during the early life of the pavement. Relationships between mechanical properties of bituminous mixtures and age have been established. The results make it possible to take into account the effect of aging during pavement evaluation and during characterization of mixes with respect to aging properties. It was shown that stiffness modulus and creep deformation of bituminous layers can change significantly during the early life of the pavement and that this change should be considered in performance specifications and pavement analysis.